Stencil sheet and coating solution therefor



Patented Mar. 30, 1926.

UNITED STATES v 1,578,960 PATENT orrlca.

max BROOKING DAVIS, or cmcnm'arr, 01:10; ASSIGNOR TO A. 28. mo: comm.

. or cmcaeo, n-mnors, A coaroaa'rrou or rumors.

STENCIL SHEET AND COATING SOLUTION THEREFOR.

Io Drawing.

To all whom it may concern Be it known that I, ALEX BROOKING DAVIS, a citizen of the United States, residing at Cincinnati, in the county of Hamilton and State of Ohio, have invented certain new and I useful Improvements in Stencil Sheets and Coating Solutions Therefor, of which the following is a specification. I

My invention relates particularly to typeim 'ressible stencil-sheets of the sort in which is employed a porous base such as Yoshino having an ink-impervious coating which ma be stencilized by pressure such as impact 0 type and the like thereon. My.

0b]ect is to produce a stencil-sheet which can be manufactured easilyand at low cost, which may be readil stencilized, which will be stable and dura 1e and from which a large number of prints of high quality may be obtained. I have found that the esters of starch, both the aromatic and the aliphatic or fatty esters, possess properties which adapt them for stencil use, some of them particularlywhen modified by the addition of a suitable agent such, for example, as a non-volatile material soluble in the same solvent as that employed to dissolve the starch ester.

In carryin ferred form of starch such as starch acetate. This may be prepared by acetylating purified corn starch with acetic anhydride in the proportion of 450 pounds of starch to 750 pounds of acetic anhydri-de in the presence of a catalizer and a solvent. As a solvent xylol is suitable. Starch acetate so prepared is water-insoluble but almost, completely soluble in acetone. In fact, the solution is so complete as to leave only a faint opal'escence as an indication of aminute quantity of insoluble material remaining. Ordinarily such acetate alone and without modification would set upon the base sheet in a film too hard for easy stencilizatio n-a difficulty which. may be overcome by employing .a higher starch ester. I prefer, however, to

out my invention in a preacid or the li e. Some of'these are crystalline in structure,fwhich I consider objectionable and while other substances may be added to prevent their crystallization I pre-fv may employ a fatty acid ester 10y the starch ester above described and.

Application filed July 3, 1925. 'Serial No. 41,436.

fer to employ phenolic esters of phos horic acid, which are non-er stalline and 0 these excellent results may e obtained by using tr1cresy1 phosphate. Other non-volatile or substantially non-volatile modif ing or softenlng agents may be employe to give an nternal lubricating efiect, thereby promotmg ease of stencilization and a number of esters of both the aromatic and the aliphatic series will answer for this purpose but I prefer to employ butyl tartrate. Lubricants other than esters may, however, be employed and W111 give goods results.

As a specific illustration of a practice of my. invention the following directions will serve: grams of starch acetate,- preferably prepared as above pointed out, are dissolved in 90 c. c. of acetone at the boiling point of the acetone. Into this solution there mav be dpoured 35 grams of tricresyl phosphate 20 c. c. of butyl tartratetogether, if it be desired to color the mixture, with a suitable (preferably acetone-soluble) dyestulf. The solution may then be allowed to cool to ordinary temperature. Then, the solution being conta ned in a suitable pan, sheets of Yoshmo may be floated upon or drawn over the surface of the soluton, excess thereof being removed and returned-to the pan by drawing the sheets, after impregnation, over a taut wire. The sheets may then be hung up to cure, 1. e. to permit the volatilization of the acetone, which requires but a few hours. Yoshino being coated or impregnated with a homogeneous, 'type-impressible substance, mainly of highly dispersed starch acetate.

It is, of course, obvious that starch acetate can be acetylated to a hi her or lower degree than as above indicate and that, if

1a A type-impremible stencil-sheet consisting of a porous base having a coating including a starch ester.

2. A type-impressible stencil-sheet consistm of a porous base having a coating mclu ing starch acetate.

' 3. A. type-impressi They are then ready for use, the

ble stencil-sheet con-.

io :I and a In ricating-agent.

' of a porous base sheet having a coatg a starch ester and a Softening of a porous base having a coating Gi i .11 nt inclu starch acetate, a softening agent and a In ricating agent. a

7. A type-impressible stencil-sheet conmg including starch acetate and a phosphoric acid ester.

' 8. A type-impressible stencil sheet consisting of a porous base sheet having a coating including starch acetate and" tricresyl:

phosphate.

9. A type-impressible stencil-sheet consisting of a porous base sheet having a coatincluding starch acetate, 9. phosphoric acid ester and butyl tartrate. V 10. A type-impressible stencil-sheet 'conpressible stencil-sheet con--' .6. A tgpedefining) a porousbase having a coating 'sisting of a porous base sheet having a coating including starch acetate, tricresyl phosphate and butyl tartrate.

11. A solution for coating type-impressible stencil-sheets consisting of starch acetate dissolved in acetone, to which has been added a phosphoric acid ester." 4

12. A solution for coating type-impressible stencil-sheets consisting of starch acetate dissolved in acetone, to which has been added a phosphoricacid ester and an aliphatic ester. j

13. A solution for coating type-impressible stencil-sheets consisting of starch acetate dissolved in acetone, to which has been .added tricresyl phosphate and butyl tartrate.

14. A solution for coating type-impressible stencil-sheets consisting of starch acetate dissolved in acetone, to which has been added tricresyl phosphate and a lubricant.

15. A solution for coating type-impres- 'sible stencil-sheets consisting of starch acetate dissolved in acetone, to which has been added tricresyl phosphate, a modifier and a lubricant.

This specification signed and witnessed this 29th day of June, 1925.

ALEX BROOKING DAVIS. 

